This invention relates to novel multipurpose triazine-containing multisilane compounds useful as coupling agents, adhesives, protective coatings and the like; to fillers and glass fibers coated with the coupling agents; to a process for preparing the compounds; and to glass fiber reinforced (GFR) composites in which such coated glass fibers in the form of yarns, cords, strands, and fabrics, collectively referred to herein as "glass fibers" or simply "fibers" for brevity, are used.
The multisilane compounds are obtained by a reaction of cyanuric chloride with an aminoalkyl-alkoxysilane or alkyl-aminoalkyl-alkoxysilane, together referred to as "alkoxysilanes" for brevity.
It is suggested that bis-trimethoxysilyl coupling agents provide increased crosslinking of the coupling agent in the interface region by creating six (6) crosslinking sites--double that of a conventional trialkoxysilane coated filler--hence result in improved adhesion. See "Surface Modifiers: They are Becoming More Versatile" by P. A. Toensmeier Modern Plastics pg 55 May 1987. This is attributed to multiple bonding of atoms, which creates a surface adhesion expected to be not only strong but moisture- and corrosion- resistant. Though the bonds are hydrolyzable, equilibrium is such that they reform easily, and the additives can be used in any resin using silanes.
This invention specifically provides a multisilane which provides at least nine (9) crosslinking sites, and has several other advantages which make it an exceptional coupling agent.
More specifically, this invention relates to multisilane coupling agents employed in a sizing composition for glass fibers and other siliceous fillers having analogous reaction characteristics. It will be recognized that fibers are a particular form of filler used in those instances where reinforcement is sought to enhance the inertness, strength and other physical charateristics of a reinforced solid synthetic resinous material. For example, an essential characteristic of the such fillers is that chemical groups on their surface are hydrophilic so that only a weak bond can be established between the synthetic resin and the surfaces of the fibers. Such bonding as is established is vitiated by immersion in water, or even by exposure to high humidity. To enhance the bonding relationship a plethora of anchoring or coupling agents and sizing systems have been used, none of which are more relevant than the disclosure of the bis-trimethoxysilyl coupling agents which focussed the desirablity of providing several crosslinking sites.
It must be borne in mind that a coupling agent alone provides neither adequate lubricity or bonding for processing fibers, nor adequate protection against destruction of the fibers' surfaces by mutual abrasion. Hence it is necessary to employ the coupling agent in a dilute aqueous "size" which is applied to the fibers in a well known manner so as to provide a thin coating, typically less than 1 micron thick. It is in such sizing compositions that the coupling agents of this invention, prepared in an aqueous medium, are used.
To promote adhesion between other than a glass fiber surface and a solid organic polymer, for example a polycarbonate, the coupling agents may be prepared in an essentially anhydrous medium and applied to the surface which may then be secured to the polycarbonate. However, some resins, such as rigid poly(vinyl chloride) (PVC) are notably far more difficult to bond to other surfaces, particularly large glass or metal surfaces PVC is also particularly difficult to reinforce with glass fibers than other resins, for well known reasons set forth in U.S. Pat. No. 4,536,360 to D. Rahrig, and the multisilanes are unique in that they provide performance comparable to that obtained with the conventional alkoxysilanes used in the '360 patent. Such comparable performance is obtained because these multisilanes are able to interact with PVC through the same chemistry as that delineated in the Rahrig '360 patent, namely generation of an allylic chlorine (Cl) moiety in the vinyl chloride chain.